Motion Detection and Analysis using Multimaterial Fiber Sensors

Abstract

We present the design of a motion analysis wearable sensor based on a flexible and stretchable fiber sensor coupled to a miniaturized wireless electronic circuit. The fiber is made of carbon nanotubes and polydimethylsiloxane elastomer (PDMS) and, when integrated into a smart garment, it enables to measure motion and multiple vital signs. The performance of the fiber is thoroughly characterized and benchmarked for motion detection and analysis (i.e. flexion/extension and angular amplitude). The measurements were performed by mean of a developed electronic circuit designed to interface with the fiber and to digitize and transmit the data wirelessly. It can read the changes in the fiber impedance with an error of less than 0.2% and an accuracy of ±10Ω. The system is first validated using a robotic arm, and then utilized to measure motion on the knee joints of two volunteers. The results show that the system including the fiber sensor and the interface circuit can detect movements between 0.2 Hz and 1 Hz (with an accuracy of 99.05% for the robotic arm and 95.98% for the knee joint). Low to excellent correlations between the signal amplitude and the angular amplitude of the movement were found.